[syslinux] [PATCH] efi: leaving long mode in kernel_jump routine

[Thomas Letan]

Hi.
Great news it works! I myself didn't had the time to test yet (I was on
holidays) so thank you.

I will try to test on monday a 64bits kernel.

Thomas

Le 24/08/2015 16:27, Patrick Masotta a écrit :>
>  > On Tue, Aug 4, 2015 at 2:55 AM, Thomas Letan via Syslinux
<syslinux at zytor.com> wrote:
>  > Syslinux 6.03 (efi64) fails to boot a 32-bit kernel. The way Syslinux
>  > leaves long mode in kernel_jump assembly routine does not follow AMD64
>  > specifications. More precisely:
>  > 1. After setting a new GADT, `cs` has to be refresh by doing a long
>  > jump, but it is not
>  > 2. Other segments have to be updated, but they are not
>  > 3. Disabling paging has to be done before disabling long mode, but the
>  > implementation does the opposite
>  >
>  > In most cases, a computer that tries to execute the kernel_jump routine
>  > reboot (it can also hangs). This patch fixes the kernel_jump routine.
>  >
>  > Signed-off-by: Thomas Letan <thomas.letan at ssi.gouv.fr>
>  > ---
>  >  efi/x86_64/linux.S | 61
>  >
>  ++++++++++++++++++++++++++++++++++++------------------
>  >  1 file changed, 41 insertions(+), 20 deletions(-)
>  >
>
> I can just confirm this patch:
> 1) it is needed.
> 2) it solves the problem.
> 3) so far not regression detected.
>
> Test:
> Client Hardware: HP 2570P
> Boot Mode:        PXE EFI64
> Target OS:         ubuntu-15.04-desktop-i386.iso
>
> Trying to PXE boot "ubuntu-15.04-desktop-i386.iso" on an EFI64
> platform quietly aborts after transferring initrd.lz.
> After applying the present patch "ubuntu-15.04-desktop-i386.iso"
> booted normally. The normal booting of AMD64 based OSs looks
> unaffected by the patch.
>
> Best,
> Patrick
>
>